of going out with a dude since although I'm biromantic I'm only sexually attracted to girls. There's this one cute guy in my class who's amazing, every time I look at him I smile, etc. and if he was gay/bi (he's a very shy dude so he doesn't talk about this) and I was a little older (don't see the point of dating at my age, only 13) I would want to ask him out, but the reason I'm afraid is I imagine it would end very quickly since there's bound to be a girl that I am way more attracted to since the sexual attraction is added in. Plus dating in general would be troublesome for me when taking into account the future since there's going to be times where I feel like and present like one gender and times where I feel like and present like another. Overall I'm kind of screwed in the romance department however I see that many people are able to overcome stuff like this so I have faith.
You said yourself you're only 13. I think you shouldn't worry so much about relationships at your age. As far as your gender identity goes, there's different people who like different things. There's going to be someone who is perfectly fine with who you feel you are.
I agree, you could see if he's interested in dating, and just see what happens, where it goes, just have fun with it. You could end up best friends. It's not like you have to be looking for a relationship that's going to last for ever, and I don't think trying to do that would be a great idea anyway. But I can definitely relate to your fears. I've definitely had some anxiety about being with someone that I could be romantically, but not sexually attracted to. Not because I'm sure I'll want someone else, but because eventually, they'll want sex and I can't deliver, and they'll get all angry and disappointed. Communication is key, that's all I can say.